// 元素居中
center()
	if !arguments[1]
		position absolute
	else
		position arguments[1]
	if arguments[0] == 'x'
		left 50%
		transform translate(-50%, 0)
	else if arguments[0] == 'y'
		top 50%
		transform translate(0, -50%)
	else
		top 50%
		left 50%
		transform translate(-50%, -50%)

// 方形
square()
	width arguments
	height @width  

rem()
	return 1rem if !arguments[0]
	return (arguments[0] / 24)rem (arguments[1] / 24)rem if (arguments[1])
	return (arguments[0] / 24)rem

em()
	return 1em if !arguments[0]
	return 1px if arguments[0] <= 1 && arguments[0] >=0
	return (arguments[0] / arguments[1])em if arguments[1]
	return (arguments[0] / 24)em

per()
	return 100% if !arguments[0]
	return (arguments[0] / arguments[1] * 100%) if arguments[1]
	return (arguments[0] / 720 * 100%)
	
circle()
	border-radius 50%

ellipsis()
	overflow hidden
	text-overflow ellipsis
	if arguments
		display -webkit-box
		-webkit-line-clamp arguments[1] ? arguments[1] : 2
		-webkit-box-orient vertical
	else
		white-space nowrap